二十二碳六烯酸乙酯对沙土鼠缺血再灌注脑损伤及水肿作用的研究

研究二十二碳六烯酸乙酯(E-DHA)对沙土鼠缺血再灌注脑损伤及其脑水肿的影响.选用雄性断奶沙土鼠灌胃给予二十二碳六烯酸乙酯(150 mg/(kg·d))或等体积溶媒10周,阻断沙土鼠双侧颈总动脉血流10 min,造成缺血再灌注模型;测定再灌注后脑组织中丙二醛(MDA)水平,还原型谷胱甘肽(GSH)含量,超歧化氧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-PX)和钾、钠-ATP酶(Na ,K -ATPase)活性,脑水含量,钠、钾离子浓度及海马CA1区神经细胞存活百分数.结果表明:E-DHA预处理显著降低缺血再灌注沙土鼠脑组织MDA水平,阻止GSH含量、GSH-PX和Na ,K -ATPase活性下降,而对SOD的活性未表现出明显作用;E-DHA亦调节缺血再灌注沙土鼠脑组织钠、钾离子浓度,减轻缺血再灌注所致的脑水肿和神经细胞死亡.提示E-DHA对脑缺血再灌注脑损伤有显著保护作用,机制可能其与抗氧化作用有关.     

基于数据矩阵分解的相干源方向估计新方法

提出一种相干源存在情况下的波达方向估计新算法。利用阵列快拍数据构造数据矩阵,相关去噪后,通过奇异值分解获得低维信号子空间的估计,然后运用ESPRIT思想估计出波达方向。无论是否存在相干源,新算法均能有效估计出波达方向,并且无需角度搜索,运算量小。该算法虽基于一维线阵,但可直接推广到具有线性性质的二维平面阵,如L形阵、十字阵、双平行线阵等。计算机仿真验证了算法的有效性     

2-D连续-离散系统的平衡模型降阶

基于局部能达性与局部能观性的分析给出2-D连续-离散系统状态空间模型的平衡实现,这一实现的第i个状态分量的重要性由系统的能达、能观阵的第i个对角元素所度量,去掉平衡实现系统弱能达、弱能观的部分,从而得到2-D连续-离散系统的模型降阶。所给示例表明,该方法具有良好的降阶效果。     

带涡产生器的圆管管片式换热器流场及温度场的数值分析

用数值方法分析了涡产生器式圆管管片式换热板芯单个圆管单元区域内的速度场和温度场.计算结构针对某实际换热器结构,S1=20 mm,S2=15.5 mm,tp=2.5 mm,涡产生器攻角为45.°计算时选取雷诺数范围为500~20 000,选取R e=1 000和10 000时的计算结果进行了讨论和分析.涡产生器产生的纵向涡旋增强了圆管尾流区流体的掺混和能量交换,并带动尾流区流体及时向下游流动.与平片翅片结构比较,涡产生器式圆管管片式换热板芯尾流区流体与壁面温差增大,有利于增强换热.     

组合数丢番图方程[2x]=[4y]的正解

运用递推序列法，给出组合数丢番图方程[x2]=[y4]的一个初等解法．     

浅谈中国企业战略问题

中国企业陷入无战略危机的原因是脱离中国企业的现实环境,一味借用并参照西方主流的战略理论来看待自身的战略实践,中国企业已进入开放下的全面竞争阶段,应当适时的形成扎实的系统管理能力,养成战略导向思维,与中国企业的现实环境相匹配,实施灵活的战略和战略管理过程。     

Optimization in the Migration Problem of Mobile Agents in Distributed Information Retrieval Systems

In this paper,we employ genetic algorithms to solve the migration problem (MP).We propose a new encoding scheme to represent trees,which is composed of two parts;the pre-ordered traversal sequence of tree vertices and the children number sequence of corresponding tree vertices.The proposed encoding scheme has the advantages of simplicity for encoding and decoding,ease for GA operations,and better equilibrium between exploration and exploitation.It is also adaptive in that,with few restrictions on the length of code,it can be freely lengthened or shortened according to the characteristics of the problem space.Furthermore,the encoding scheme is highly applicable to the degreeconstrained minimum spanning tree problem because it also contains the degree information of each node.The simulation results demonstrate the higher performance of our algorithm,with fast convergence to the optima or sub-optima on various problem sizes.Comparing with the binary string encoding of vertices,when the problem size is large,our algorithm runs remarkably faster with comparable search capability.     

Numerical tests of efficiency of the retrospective time integration scheme in the self-memory model

A set of numerical tests was carried out to compare the retrospective time integral scheme in a self-memory model,whose dynamic kernel is the barotropical quasi-geostrophic model, with the ordinary centered difference scheme in the barotropical quasigeostrophic model. The Rossby-Haurwitz wave function was taken as the initial fields for both schemes. The results show that in comparison with the ordinary centered difference scheme, the retrospective time integral scheme reduces by 2 orders of magnitude the forecast error, and the forecast error increases very little with lengthening of the time-step. Therefore, the retrospective time integral scheme has advantages of improving the forecast accuracy, extending the predictable duration and reducing the computation amount.     

辐照对长江可培养微生物的影响及挑选指示微生物

以长江中下游区域的水体为研究对象,通过分离纯化手段,对不同辐照剂量下长江水样中可培养微生物种类、数量进行研究.结果显示:辐照引起可培养微生物数量大幅下降,但可培养微生物群落结构变得更加丰富.各菌属中,黄杆菌属(Flavobacterium)受辐照影响最大,培养得到的菌落比例下降了28.98%,芽孢杆菌属(Bacillus)对辐照耐受性极强,菌落比例上升了15.78%.同时发现了长江水体中具有指示价值的微生物d(Flavobacterium nitratireducens strain N1),为放射性污染的生物监测提供相关参考依据.     

Secure Transmission Scheme for Parallel Relay Channels Based on Polar Coding

This paper considers the use of polar codes to enable secure transmission over parallel relay channels.By exploiting the properties of polar codes over parallel channels, a polar encoding algorithm is designed based on Channel State Information(CSI) between the legitimate transmitter(Alice) and the legitimate receiver(Bob).Different from existing secure transmission schemes, the proposed scheme does not require CSI between Alice and the eavesdropper(Eve). The proposed scheme is proven to be reliable and shown to be capable of transmitting information securely under Amplify-and-Forward(AF) relay protocol, thereby providing security against passive and active attackers.